rebase: keep original mq patch format (Issue1574)
Rebase now doesn't make assumptions about which format has been
used for a mq patch (git or normal).
Before finalizing a patch it keeps track of the original format,
by reading its header, and then restores the format when reimporting
it.
This way it also allows for having mixed styles.
Note: this version corrects a failure in the test
#!/bin/sh
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i